Pall Corporation

Warren M Foss

Peter J Degen

Thomas C Gsell

David B Pall

Irving B Joffee

The present invention provides a polymeric, particularly aramid, fiber filtration sheet having a relatively small pore size and high pore uniformity. The present inventive aramid fiber filtration sheet preferably has a titer reduction against bacteria such as Pseudomonas diminuta. The present invention also provides a method of preparing reduced-diameter aramid fibers, as well as a method of preparing an aramid fiber filtration sheet from such reduced-diameter aramid fibers. The present invention further provides a method of treating a fluid by passing a fluid through the present inventive aramid fiber filtration sheet, as well as a filter element incorporating the present inventive aramid fiber filtration sheet.

Aramid fiber filtration sheet

Filter media comprised of charge modified, resin coated inorganic microfibers are prepared by mixing inorganic microfibers with an aqueous solution of a water soluble, noncolloidal cationic thermosetting binder resin to form a dispersion, following which a precipitating agent is added to precipitate the binder resin and coat the microfibers. The coated microfibers may be used in the dispersed or suspended form as a filter aid. Preferably they are formed into a filter sheet which is then dried and cured to form a filter sheet of narrowly distributed pore size, pore sizes as small as one-half micron, and having a positive zeta potential in alkaline media. Glass is the preferred microfiber and polyamine-epichlorohydrins the preferred resins. By providing the normally negative zeta potential microfibers with a positive zeta potential the binder resins used to coat the microfibers substantially enhance particulate removal capabilities of the microfiber filter sheet.

Charge-modified microfiber filter sheets

A process for making a porous, fibrous structure coated with a fluorocarbon polymer comprising (1) preparing an aqueous slurry of inorganic fibers and fluorocarbon polymer; (2) precipitating the fluorocarbon polymer onto the inorganic fibers by lowering the pH of the slurry to an acidic value and adding a cationic flocculant; (e) forming a porous, fibrous structure from the resulting slurry; and (4) drying and heat treating the resulting structure. The porous, fibrous structure comprises inorganic fibers the surfaces of which are coated with a precipitated fluorocarbon polymer with the fibers secured to one another at cross-over points by the fluorocarbon polymer thereby providing structural integrity.

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Glen Cove, NY, United States of America

Warren M Foss